1. Field of the Invention
The present invention relates to novel compounds having angiotensin type 1 (AT1) receptor antagonist activity and neprilysin-inhibition activity. The invention also relates to pharmaceutical compositions comprising such compounds, processes and intermediates for preparing such compounds and methods of using such compounds to treat diseases such as hypertension.
2. State of the Art
The aim of antihypertensive therapy is to lower blood pressure and prevent hypertension-related complications such as myocardial infarction, stroke, and renal disease. For patients with uncomplicated hypertension (for example, no risk factors, target organ damage, or cardiovascular disease), it is hoped that reducing blood pressure will prevent development of cardiovascular and renal comorbidities, conditions that exist at the same time as the primary condition in the same patient. For those patients with existing risk factors or comorbidities, the therapeutic target is the slowing of comorbid disease progression and reduced mortality.
Physicians generally prescribe pharmacological therapies for patients whose blood pressure cannot be adequately controlled by dietary and/or lifestyle modifications. Commonly used therapeutic classes act to promote diuresis, adrenergic inhibition, or vasodilation. A combination of drugs is often prescribed, depending upon what comorbidities are present.
There are five common drug classes used to treat hypertension: diuretics, which include thiazide and thiazide-like diuretics such as hydrochlorothiazide, loop diuretics such as furosemide, and potassium-sparing diuretics such as triamterene; β1 adrenergic receptor blockers such as metoprolol succinate and carvedilol; calcium channel blockers such as amlodipine; angiotensin-converting enzyme (ACE) inhibitors such as captopril, benazepril, enalapril, enalaprilat, lisinopril, quinapril, and ramipril; and AT1 receptor antagonists, also known as angiotensin II type 1 receptor blockers (ARBs), such as candesartan cilexetil, eprosartan, irbesartan, losartan, olmesartan medoxomil, telmisartan, and valsartan. Combinations of these drugs are also administered, for example, a calcium channel blocker (amlodipine) and an ACE inhibitor (benazepril), or a diuretic (hydrochlorothiazide) and an ACE inhibitor (enalapril). All of these drugs, when used appropriately, are effective in the treatment of hypertension. However, patient compliance remains an issue and physicians often prescribe agents on the basis of a benign side-effect profile, at the expense of agents with similar or marginally improved efficacy. As a result, it is believed that only 50% of treated hypertensive patients achieve satisfactory blood pressure control.
In addition, each of the major classes of antihypertensive agents have some drawbacks. Diuretics can adversely affect lipid and glucose metabolism, and are associated with other side effects, including orthostatic hypotension, hypokalemia, and hyperuricemia. Beta blockers can cause fatigue, insomnia, and impotence; and some beta blockers can also cause reduced cardiac output and bradycardia, which may be undesirable in some patient groups. Calcium channel blockers are widely used but it is debatable as to how effectively these drugs reduce fatal and nonfatal cardiac events relative to other drug classes. ACE inhibitors can cause coughing, and rarer side effects include rash, angioedema, hyperkalemia, and functional renal failure. AT1 receptor antagonists are equally effective as ACE inhibitors but without the high prevalence of cough.
Neprilysin (neutral endopeptidase, EC 3.4.24.11) (NEP), is an endothelial membrane bound Zn2+ metallopeptidase found in many tissues, including the brain, kidney, lungs, gastrointestinal tract, heart, and peripheral vasculature. NEP is responsible for the degradation and inactivation of a number of vasoactive peptides, such as circulating bradykinin and angiotensin peptides, as well as the natriuretic peptides, the latter of which have several effects including vasodilation and diuresis. Thus, NEP plays an important role in blood pressure homeostasis. NEP inhibitors have been studied as potential therapeutics, and include thiorphan, candoxatril, and candoxatrilat. In addition, compounds have also been designed that inhibit both NEP and ACE, and include omapatrilat, gempatrilat, and sampatrilat. Referred to as vasopeptidase inhibitors, this class of compounds are described in Robl et al. (1999) Exp. Opin. Ther. Patents 9(12): 1665-1677.
There may be an opportunity to increase anti-hypertensive efficacy when combining AT1 receptor antagonism and NEP inhibition, as evidenced by AT1 receptor antagonist/NEP inhibitor combinations described in WO 9213564 to Darrow et al (Schering Corporation); US20030144215 to Ksander et al.; Pu et al., Abstract presented at the Canadian Cardiovascular Congress (October 2004); Gardiner et al. (2006) JPET 319:340-348; and WO 2007/045663 (Novartis AG).
Recently, WO 2007/056546 (Novartis AG) has described complexes of an AT1 receptor antagonist and a NEP inhibitor, where an AT1 receptor antagonist compound is non-covalently bound to a NEP inhibitor compound, or where the antagonist compound is linked to the inhibitor compound by a cation.
In spite of the advances in the art, there remains a need for a highly efficacious monotherapy with multiple mechanisms of action leading to levels of blood pressure control that can currently only be achieved with combination therapy. Compounds having either AT1 receptor antagonist or NEP inhibitory activity are known, but no single compound having both AT1 receptor antagonist and NEP inhibitory activity has been reported. Thus, although various hypertensive agents are known, and administered in various combinations, it would be highly desirable to provide single compounds having both AT1 receptor antagonist activity and NEP inhibition activity in the same molecule. Compounds possessing both of these activities are expected to be particularly useful as therapeutic agents since they would exhibit antihypertensive activity through two independent modes of action while having single molecule pharmacokinetics.
In addition, such dual-acting compounds are also expected to have utility to treat a variety of other diseases that can be treated by antagonizing the AT1 receptor and/or inhibiting the NEP enzyme.